Electric marking



Patented Aug. 12, 1952 ELECTRIC MARKING Leopold Pesscl, Springfield Township, Montgomery County, ration of America,

Pa., assignor to Radio Corpoa corporation of Delaware No Drawing. Application December 3, 1948, Serial No. 63,448

42 Claims.

This invention relates to markings, and more particularly to markings produced by the passage of electric currents.

Up to the present time many suggestions have been made for techniques to produce markings electrically. Such techniques ar especially desirable for producing or reproducing intelligence at a distance. In facsimile system for example, an image may be scanned to produce an electrical signal sequence which is transmitted to one or more distant locations. There the electrical signals can be passed through portions of a carrier holding electrically sensitive material which changes in color or appearance upon th passage of an electric current. The retracting of the original scanning sequence over the carrier in synchronism with the signal sequence, will reproduce the original image. However all prior colorchange-producing arrangements were either deficient as to contrast between the unchanged and changed appearances or were unstable enough to cause a gradual color change in the unmarked background or a reversal of the desired completed color change upon exposure to the environment. It was accordingly difficult to effect permanent marking of high contrast Without resorting to elaborate copying procedure.

Among the objects of this invention the electrical production of substantially permanent marks, as well as novel materials on which such marks can be formed.

Additional objects of the invention include novel and simple techniques for electrically producing marks on a background. that is substantially incapable of fading.

Further objects of the invention include novel methods and materials for producing such marks.

Still further objects of the invention ar novel preparations and methods for electrically producing marks which do not require the electrical conductivity of the current-carrying materials to be increased.

The above as well as other objects of the invention will be more readily understood from the following description of several exemplifications.

According to the invention, marking of highly stable character is produced by passing an electric current through a dispersion of an acetylide that is decomposable through shock excitation to deposit free carbon by rupture of the acetylene linkage C-=-C-. The dispersion is held by a carrier which contrasts in appearance with the black developed by this formation of carbon.

It has been found that the production of substantially permanent marks on a substantially non-fading background by means of the electrical decompositionof acetylides is highly practical and effective. The invention is based on the fact that compounds containing the triplebond acetylide linkage -CEC- are quite sensitive to shock and readily decompose in response to suitable stimuli, liberating free carbon. The acetylide decomposition is of such character as not to appreciably affect other substances in contact with the decomposing acetylide. The liberated carbon is a black solid of permanent-character, whereas before decomposition the acetylide is of contrasting appearance and is also fairly stable and immun to general environmental effects. Some acetylides are white, others substantialiy colorless, still others being colored, but all are highly contrasting with respect to black carbon. Thus silver acetylide is white, and copper acetylide is red, but the decomposition of either acetylide produces a deep rich black.

The characteristic acetylide decomposition characteristic is exhibited by acetylen itself, which is the simplest acetyli-de-type compound, and which could be used in accordance with the invention were it not for the fact that it is a gas at normally available temperatures. The substitution of one or both of the acetylene hydrogens by other substituents or radicals avoids this difliculty so that substituted acetylenes, that is acetylides, are suitable. Among the most effective acetylides from the point of view of this invention, are the metal acetylides inasmuch as they are fairly stable and yet exhibit a relatively high sensitivity to temperature elevation. Acetylides being old and Well-known compounds, no extensive description of their properties or methods of preparation are here required. Thesecan be readily determined from the reported literature. Reference is specifically made to The Chemistry of Acetylene, a text written by J. A. Niewland and R. R. Vogt and copyrighted 1945 by the Reinhold Publishing Company, chapter II (pp. 40-70), which describes many acetylides and processes for making them.

The stabilities of the different 'acetylides' vary somewhat. Th acetylides of the metals in the B families of groups 1, 2, 3, 4 and 5 of the periodic system appear to the among the most stable. They also have the added advantage of depositing black finely divided metal particles in addition to carbon, when they decompose. The finely divided metal increases the contrast of the marks made.

The acetylides of the invention are dispersed along a self-supporting carrier to reduce the spread of the decomposition from a zone being marked to the surrounding regions. To further inhibit such spreading, relatively inert materials such as starch, powdered talc, powdered silica, etc. are included in the dispersion. These materials apparently act as diluents by absorbing the energy liberated during the decomposition at any one spot and thereby confine th decomposition to the zone subjected to the proper marking influence. The proportion of diluent used may be varied to compensate for the different sensitivities of the various acetylides or of difierent batches of the same acetylide.

The carrier may be a sheet, web, band or film of any suitable composition. Paper, or other interfelted fiber type of carrier, is especially effective because it can be obtained with a white appearance contrasting sharply with the black markings produced. Cellulosic or plastic carriers are also convenient bein light in appearance, simple to use and relatively permanent in character. Some examples are films of regenerated cellulose, cellulose acetate, nitrocellulose, polymerized methacryla-te esters, polyamides, etc. The films may be plasticized in accordance with com ventional practice, to provide the desired manipulative characteristics.

The acetylide is dispersed along th carrier by applying it as a coating on one of its surfaces or byincorporating it in the carrier body. The incorporation may be adjacent a surface so as not to unduly obscure the marks produced, where the carrier is not transparent. If desired both incorporation of, and coating with, the acetylide marking composition are combined especially for greater marking intensity.

Interfelted fiber webs such as paper sheets or tapes are especially convenient for carrying the acetylide dispersion. In addition to the white background that can be furnished by paper, the acetylide can very simply be incorporated into or over the web during its manufacture. Thus the acetylide mixture together with bonding ingredients may be applied to the web as it leaves 'the'final calender or drier. Alternatively the mixturemay be added to a surface layer of the partially formed web while it is still on the wet end of a Fourdrinier forming wire, so that the acetylide becomes imbedded within the carrier. The type of bonding ingredients used is not limited. Starch, casein, glue, gums, resins such as polyvinyl alcohol, sodium carboxy methyl cellulose, partially polymerized thermosetting or thermoplastic resins are examples of suitable bonding agents.

According to one phase of this invention, a metal acetylide is formed in situ in an absorbent carrier such as paper. The carrier is impregnated with an aqueous solution of the desired metal in reactive form and is then exposed to acetylene. Reaction takes place between the acetylene and the metal to deposit the metal acetylide within the carrier.'

As an example of silver acetylide dispersion in a carrier, a 2 percent solution, by weight, of silver nitrate in water, is prepared and a concentrated ammonia solution is added till the resulting precipitate of silver oxide just redissolves. The paper carrier is then impregnated with the final solution and exposed to acetylene gas. After a few minutes, the treated paper is removed and dried. If desired any unreacted soluble silver compounds may be washed out before or after-drying to diminish the light- 4 sensitivity and undesired premature darkening. A bonding mixture may be applied to the paper to anchor the acetylide more adherently to the fibers and keep them from dusting out of the dried paper. The carrier is easily prepared in a continuous process involving the above steps.

The production of marks on the prepared carrier is effected by passing an electric current through a diminutive portion of the carrier and then moving the passage of current along a carrier zone corresponding to the indicia to be marked. Alternating or direct current is suitable inasmuch as the heat generated by the passage of either type of current is sufficient to shock the acetylide into decomposition at the current carrying portion of the acetylide carrier. Furthermore the marking current may be conductive or capacitive.

For improving the passage of conductive marking current, the conductivity of the carrier and/or the acetylide dispersion is increased but the conductivity should not be so high as to reduce the heating effect of the current. One convenient technique is to arrange that the marking current is electrolytic. For this purpose the carrier may be impregnated with an aqueous solution of an electrolyte such as sodium chloride, sodium sulfate, sodium nitrate, am monium nitrate, ammonium sulfate, etc. As shown in U. S. Patent No. 2,225,247, granted December 17, 1940, electrolytes such as the last three recited, impart sufiicient conductivity to a dry carrier, if exposed to a moist atmosphere so that the impregnated carrier may be used in substantially dry form. Some electrolytes can be used with non-aqueous solvents in place of water. See U. S. Patents numbered 2,181,533, granted November 28, 1939; 2,229,091, granted January 21,- 1941; and 2,251,742, granted August 8, 1941. Electrolytically conducting solid solutions of electrolytes, as described in U. S. Patent No. 2,283,558, granted May 19, 1942 are also suitable.

The carrier may also contain conductive material such as metal particles which may be incorporated during the formation of the carrier. Such conductive material can be used by itself or together with the electrolytically conductive mixtures. One effect of the improvement in conductivity where the marking current is conductive, is to improve the definition and sharpness of the mark, apparently by restricting the spread of the marking current through the carrier and assisting the current in taking the shortest path between the current-applying electrodes.

Any suitable apparatus may be used to apply the conductive marking current and the marks may even be made by manually moving an electrode connectedto one terminal of a current source over one face of a carrier sheet resting with its other face against an extended plate electrode connected to the opposite terminal of the source. The carrier-contacting portion of the moving electrode should have an area commensurate with the fineness of the desired marks. Facsimile reproducing apparatus, such as the one shown in U. S. Patent No. 2,415,229 granted February 4, 1947, are also eifective for marking in accordance with the present invention. With this type of apparatus care should be taken not to subject the carrier to excessive friction which would cause undesired heating.

A feature of the invention is the use of capacitive currents to produce the desired marking.

By this is meant the bringing of electrodes from a high frequency current source relatively close to the carrier, on opposite faces for example, so that a relatively large high frequency voltage is developed across a diminutive portion of the carrier. With a large enough voltage there will be enough high frequency current flowing through the capacitance presented by the spaced electrodes to effectively heat the capacitor dielectric, which is essentially the carrier. By selecting carriers of relatively high power factor, that is, of high dielectric loss when used as a capacitor dielectric, the heating effect is improved. lhe incorporation into thecarrier of materials that increase its dielectric losses is also very effective to increase the generation of heat in a high-frequency field. By way of example, a carrier sheet may be rendered semiconductive by distributing through it conductive particles in a concentration low enough not to short-circuit any alternating-electric fields that may be impressed across it. Lowering the inter facial carrier resistivity from hundreds of megohms per square centimeter to about one hundredth of a megohm, or less per square centimeter is suitable. An excessive overall increase in carrier conductivity is to be avoided. The carrier'may be provided with a highly conductive stratum as by the incorporation of finely divider conductive particles to decrease the effective di electric thickness between the capacitance electrodes, thereby increasing the capacitance and concentrating the electric field within a smaller zone. Finely divided metal particl s make suitable additions for imparting either the semiconductive or relatively highly conductive characteristics. These featuresmay beused together or separately to improve the marking ability of the carrier. Electric currents with frequencies:

as low as 1 megacycle per second or even lower will produce satisfactory markings, although in general higher frequencies cause more rapid marking. The carrier should be as thin as is practicable, preferably about 0.003 inch or less.

An improved advantage of the capacitive marking is that the carrier need not be specially treated to increase its electrical conductivity and accordingly can be used in perfectly dry condition.

To render the markings of the invention more permanent, the carrier background can be treated to inactivate it against the further development of marks. The unreacted acetylides may be dissolved out as by a suitable solvent leaving a marked carrier that is about as permanent as the v carrier itself. With the metal acetylides an aqueous solution of a strong acid such as sulfuric acid is suitable. In general this removal is not necessary inasmuch as the acetylides are quite stable so long as they are kept from large thermal. or mechanical shocks. Silver acetylide exhibits the characteristic light-responsive darkening of silver compounds and requires special consideration.

According to a further phase of the invention, the carrier, either before, during or after marking, is treated with materials, such as ammonium sulfamate or ammonium phosphate, to reduce its flammability or rate of combustion. This can be arranged to offset the increase in. combustibility contributed by the presence of the acetylides'.

The capacitive marking method is not limited for use with acetylide marking compositions, but is also highly effective with any marking mate rials that are subject to a changein appearance uponabeing heated. Further examplesof thermal responsive materials that are changed in color by capacitive marking currents are the thicoxalates, mercaptides, thio-glycolates, and thiocarbamides of copper, silver, mercury and lead, as described in the Kline Patent No. 2,425,742, dated August 19, 1947.

While several exemplifications of the invention have been indicated and described above, itwill be apparent to those skilled in the art that other modifications may be made without departing from the scope of the invention as set forth in the appended claims What is claimed is:

1. A method of marking a carrier with indicia comprising the, steps of: providing a carrier with a dispersion of at least one compound containing an acetylene linkage and decomposable by shock excitation to deposit free carbon; and passing through a suitably shaped dispersion-carrying portion of the carrier an electric marking current having an intensity high enough to decompose the acetylene linkages of at least a fraction of the compound present at said carrier portion to distribute the deposition of carbon in accordance with the desired indicia.

2. A method of marking as defined by claim 1 in which the shock-decomposable compound is a metal acetylide.

3. A method of marking as defined by claim 1 in which the shock decomposable compound is an acetylide.

4. A method of marking as defined by claim 1 in which the shock-decomposable compound. is a metal acetylide having the formula M--CECR where M is a metal and R is a substituent selected from the class consisting of an organic radical, hydrogen and a metal.

5. A method of marking as defined by claim 1 in which the shock-decomposable compound is an acetylide of a metal taken from theclass consisting of the B families of groups 1, 2, 3, 4 and 5 of the periodic system.

6. A method of marking as defined by claim 1 in which the dispersion includes relatively inert diluent material for assisting in the absorption of energy released by the decomposition and preventing the decomposition at one portion of the carrier from spreading to adjacent portions.

'7. A method of marking as defined by claim 6 in which the diluent material is in finely divided powder form.

8. A method of marking as defined by claim 1, in which the carrier contains the shock-decomposable compound in a surface layer portion.

9. A method of marking as defined by claim I, in which the shock-decomposable compound is imbedded within the carrier.

10; A method of marking as defined by claim 1 in which the carrier'portion is essentially oflow electrical conductivity and has its conductivity increased before thepassage of the marking current.

11. A method of marking as defined by claim 1 in which the carrier portion is essentially of low electrical conductivity and the marking current is essentially capacitive.

12. A method of marking a carrier with indicia comprising the steps of: providing a carrier with an electrolytically conductive dispersion of at least one compound containing an acetylene linkage and decomposable by shock excitation to deposit free carbon; and passing through a suitably shaped dispersion-carrying portion of the carrier an electrolytic marking current having an intensity high enough to'decompose the acetylene linkages of at least a fraction of the compound present at said carrier portion to distribute the deposition of carbon in accordance with the desired indiica.

13. A method of marking as defined by claim 1 in which the marking current is varied in intensity over the suitably shaped portion to produce gradations in marking.

14. A method of marking as defined by claim 1 in which the carrier is a self-supporting sheet of essentially uniform characteristics and contrasting in appearance with respect to black.

15. A method of selectably marking indicia on a body of material, comprising the steps of: providing along a surface of said body a layer containing'finely divided particles of at least one compound including an acetylene linkage and decomposable by shock excitation to rupture this linkage and deposit free carbon; passing through a diminutive portion of the surface an electric current having a selectable intensity; and scanning the passage of current over an extended area of the surface while varying the current intensity for selectably decomposing the acetylene linkage and distributing the deposition of carbon over the area in accordance with the desired indicia.

16. A method of selectably marking indicia on a body of material, comprising the steps of: providing along a surface of said body a layer containing finely divided particles of at least one compound including an acetylene linkage and decomposable by shock excitation to rupture this linkage and deposit free carbon; passing through a diminutive portion of the layer an electric current having an intensity high enough to decompose at least a fraction of the compound at said portion; and scanning the passage of current over an extended zone of the surface for selectably decomposing the acetylene linkage and distributing the deposition of carbon'over the area in accordance with the desired indicia.

17. A method of marking as defined by claim 15 in which the shock-decomposable compound is an acetylide of the class consisting of silver, cadmium and zinc acetylides.

18. A method of marking as defined by claim 17 in which the particles are mixed with relatively inert diluent to inhibit the spreading of decomposition from the diminutive portions through which the marking current is passed.

19. A method of marking as defined by claim 18 in which the support is a paper web.

20. A method of marking as defined by claim 19 in which the area is prepared for scanning by being rendered electrolytically conductive.

21. A method of marking as defined by claim 19 in which the area i of low electrical conductivity and the marking current is essentially capacitive.

22. A method of marking a carrier with indicia comprising the steps of: providing at least one compound containing an acetylene linkage and decomposable by shock excitation'to deposit free carbon; dispersing said compound along a carrier; passing through a suitably shaped dispersion-carrying portion of the carrier, an electric marking current having an intensity high enough to decompose the acetylene linkage of at least a fraction of the compound present at said carrier portion to distribute the deposition of carbon in accordance with the desired indicia. I

23. The method as defined by claim 22 in which the carrier is in the form of a sheet having an observable surface and the compound is dispersed along this surface.

24. The method as defined by claim 22 in which the carrier is in the form of a sheet having an observable surface and the compound is dispersed in the body of the sheet adjacent this surface.

25. A method of preparing a carrier capable of developing marks under the influence of electric currents, comprising the steps of providing at least one compound containing an acetylene linkage and decomposable by shock excitation to deposit carbon; and dispersing said compound along a carrier.

26. A method as defined by claim 25 in which the carrier is a self-supporting band of plastic composition.

27. A method as defined by claim 25 in which the carrier is a self-supporting band of cellulosic composition.

28. A method as defined by claim 25 in which the carrier is -a self-supporting band of interfelted fibers.

29. A method as defined by claim 26in which the compound is dispersed over the surface of the band.

30. A method as defined by claim 26 in which the band is formed by shaping and the compound is dispersed in the body of the band before the shaping is completed.

31. A method as defined by claim 26 in which the compound is a metal acetylide.

32. A method as defined by claim 26 in which the compound is dispersed together with an inert diluent to inhibit the spread of decomposition between adjacent portions of the compound.

33. A method of preparing a carrier capable of developing marks under the influence of electric currents comprising the steps of preparing a porous band impregnated with an aqueous solution of a salt of a metal selected from the class consisting of the B families of groups 1, 2, 3, 4 and 5 of the periodic system; and applying to the impregnated band the vapors of a compound containing the HCEC- structure to react with the metal salt and form the corresponding acetylide.

34. In a structure capable of developing marks under the influence of electric currents, a selfsustaining base carrying a dispersion of at least one compound containing an acetylene linkage and decomposable by shock excitation to deposit free carbon by disruption of this linkage.

35. The combination as defined by claim 34 in which the base is a plastic band.

36. The combination as defined by claim 34 in which the dispersion is a coating on a surface of the base.

37. The combination as defined by claim 34 in which the dispersion is carried by a surface portion of the base.

38. The combination as defined by claim 34 in which the shock-decomposable compound is dispersed with relatively inert diluent to inhibit the spread of any decomposition induced in a localized portion.

39. The combination as defined by claim 34 in which the shock-decomposable compound'is an acetylide.

40. The combination as defined by claim 34 in which the shock-decomposable compound is an acetylide of a metal taken from the class consisting of the B families of groups 1, 2, 3, 4 and 5 0f the periodic system.

41. A method of marking a carrier comprising providing said carrier with a dispersion of at least one decomposable compound containing an acetylene linkage, and passing through a portion of said carrier high frequency electric currents of an intensity sufi'icient to generate dielectric heat losses and raise the temperature of said portion high enough to decompose said compound.

42. A method according to claim 41 in which said compound is a metallic acetylide.

LEOPOLD PESSEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,880,449 Hickman et a1 Oct. 4, 1932 2,191,867 Shore Feb. 27, 1940 2,336,229 Russell Dec. '7, 1943 2,346,670 Engler et a1 Apr. 18, 1944 2,425,742 Kline Aug. 19, 1947 2,451,331 Greig Oct. 12, 1948 OTHER REFERENCES Chemical Abstracts, vol. 20, p. 29583; vol. 27, p. 55416; vol. 28, p. 30124 (copies in Scientific Library). 

